Photolithographic technology plays an important role in the manufacture of integrated circuits (ICs) (also referred to as semiconductor chips.) Improvements in lithography have enabled the printing of smaller features of integrated circuits. This, in turn, has allowed for production of more densely populated integrated circuits and more powerful and cost-effective semiconductor devices.
However, there are times when even the most advanced techniques, e.g., use of laser light or lower wavelength light for exposure of the mask geometries, still have limitations that are unable to achieve specific designs.
Lithographic processes are often referred to by the smallest feature, which may be the line width, spacing between lines, or the distance from line tip to line tip. The smallest feature in a given lithographic process is often referred to as the “threshold,” in that the threshold distance is the smallest distance that can be produced using a certain lithographic technique. Currently, there are “20 nanometer” or “30 nanometer” technologies, which indicate that the smallest feature, which can be the width of a trace on a semiconductor device, is used as the name for that technology. So, a 20 nm process can produce a feature as small as 20 nm.
When small features are being produced, there is often a need to create a contact pad or other sub-portion of a feature that is smaller than the process limitation. This may only happen in a few places on a chip. Because such features cannot be consistently manufactured, the chip layout is redesigned to accommodate these limitations, which takes up additional semiconductor real estate and increases costs of the ICs.
It can be seen, then, that there is a need in the art to achieve sub-threshold features within a semiconductor chip.